The ability of rats to respond immunologically to allogeneic or syngeneic gamma 1F will be determined by immunization of rats with rat gamma 1F of different sources and testing for antibody by the Farr technique and for delayed hypersensitivity by skin testing. The effect of the state of immunologic reactivity upon the growth of hepatomas that produce gamma 1F will be compared to hepatomas that don't produce gamma 1F.